Melt Flow Index

The Melt Flow Index (MFI) is one of the most important rheological parameters for characterizing thermoplastic polymers. It measures the amount of molten material that flows through a standardized capillary under a defined load and at a predetermined temperature over a period of ten minutes. The result, expressed in grams per 10 minutes (g/10 min), provides a direct indication of the material’s melt viscosity and, consequently, its processability in molding, extrusion, or blow molding processes. High MFI values indicate a low-viscosity polymer that is more fluid and easier to process, while low values indicate high-viscosity materials with better mechanical properties but that are more difficult to process. Accurate knowledge of the melt flow index is essential to ensure production process stability, consistency between successive batches, and compliance with customer specifications.